Paradigm shifting for ILM peeling, prone position after vitrectomy

January 23, 2017

Peeling of the internal limiting membrane has increasingly become a dogma of surgical retina, while maintenance of the face-down positioning may become anachronistic in many cases.

Take-home: Peeling of the internal limiting membrane has increasingly become a dogma of surgical retina, while maintenance of the face-down positioning may become anachronistic in many cases.  

Reviewed by Gaetano R. Barile, MD

Certain principles in ophthalmology are long established and adhered to by surgeons, in some cases for decades. But questions regarding two surgical practices–internal membrane peeling (ILM) during vitrectomy and maintaining the facedown position after vitrectomy with gas tamponade–are now being raised.

The retina subspecialty has enjoyed significant advances resulting in improvements in anatomic and visual outcomes after vitrectomy. For example, instrumentation has improved dramatically because of engineering efforts.

Especially in retinal diseases in which superior visualization is vital, wide-angle viewing has improved the surgeon’s vantage point and dyes facilitate ILM peeling. Surgical techniques, including the use of pharmacologic adjuvants, have advanced to treat diabetic retinopathy and proliferative vitreoretinopathy among other indications, according to Gaetano Barile, MD.

The intraoperative goal in patients with vitreoretinal diseases is restoration of the retinal anatomy by removing traction from the vitreous and the retinal surface in retinal detachment, vitreomacular traction, macular holes and puckers, and retinal complications associated with longer axial lengths. In more complex cases, subretinal and intraretinal disease may need to be addressed, Dr. Barile explained.

However, Dr. Barile, professor of ophthalmology, Hofstra Northwell School of Medicine, Manhattan Eye, Ear and Throat Hospital, New York, questioned if ILM peeling and maintenance of the facedown position after vitrectomy are necessary in order to restore the retinal anatomy.  

To peel or not to peel…?

There are good reasons to stain and peel the ILM, Dr. Barile pointed out. “ILM removal might allow for improved anatomic outcomes particularly in retinal surface diseases,” he said. “The retina becomes more compliant and flexible after the ILM is removed, and its removal eliminates the scaffold for reproliferation after the procedure.”

The list goes on. Basically, peeling works, macular holes close more consistently, macular puckers recur less often, the macular thickness decreases in diabetic macular edema, there are improvements in myopic foveoschisis, and there is decreased risk of macular pucker in the presence of a primary retinal detachment.

In support of ILM peeling, Dr. Barile cited a meta-analysis (Retina 36:679–687, 2016) that summarized macular hole data. “Our success rates with macular hole surgery are very good, well above 90%,” he added. “However, with ILM peeling, the odds of recurrent macular hole formation are considerably less compared to cases in which the ILM is retained.”

Another recent study on macular pucker by Jung et al. (Retina 2016; 36:2101-2109) showed that double peeling (versus single peeling of the pucker) to include the ILM ensured complete removal of the membrane in many cases but did not necessarily improve the long-term vision. However, the authors did notice an increased incidence of inner retinal dimpling.

On the flip side of the coin, there might be good reasons to leave the ILM in place. Considerations include dye toxicity in the retina, particularly with indocyanine green, and physiologic and anatomic effects on the Muller cells and its footplates and other cells of the inner retina, possibly leading to inner retinal dimpling.

Face-down position with gas tamponades

A major factor in postoperative care following vitrectomy that surgeons have long adhered to is the face-down position after gas tamponade. Patients are instructed to maintain a face-down position for varying lengths of time postoperatively when a vitreous tamponade is injected at the end of the surgery.

Only two gases have been approved for use as tamponades, perfluoropropane and sulfur hexafluoride, C3F8 and SF6 respectively. In some cases. air is injected. The half-lives of these gases in the eye vary, but they can be long.

The advantages of using a gas tamponade with the face-down position are the temporary prevention of fluid flow through any retinal breaks and facilitation of permanent retinal adhesion, which might also improve the rate of macular hole closure. The prone positioning increases the contact by the tamponade with the desired area, Dr. Barile said.

Issues to consider with gas tamponades and prone positioning are patient compliance with the positioning and the location of the area to be tamponaded. Regarding the latter, when that area is in the inferior retina, studies have shown that inferior retinal breaks and inferior detachments do well despite the absence of contact with a tamponade, Dr. Barile pointed out.

A study that mathematically modelled the shear stress in the eye, performed by Alyward et al. (Invest Ophthalmol Vis Sci 2011; 52:7046-7051), concluded that there is very weak fluid shear stress after the vitreous is removed and this stress is lower than the adhesion strength that occurs immediately after laser retinopexy or cryotherapy. That sheer stress appears to be insufficient to detach the postoperative retina. This study indicated that in many cases, prone positioning after vitrectomy might not be necessary, Dr. Barile explained.

“In macular hole surgery, we recognize increasingly that prone positioning postoperatively likely is not necessary, especially in cases with small holes (< 400 µm],” he pointed out.  

Problems if bubble not positioned

However, there are certain cases in which problems can occur when a gas bubble is not positioned properly, i.e., those with larger tears, superior bullous detachments, residual subretinal fluid, and in eyes that are soft at the end of the surgery.

According to Dr. Barile, this can result in redundancy of the retina with a resultant “tragic” fold in the macular region following a rhegmatogenous retinal detachment that can be extremely difficult to manage.

“ILM peeling has established anatomic benefits; however, increasing questions are arising in relation to situation in which peeling should not be performed,” Dr. Barile summarized. “Care is required in cases of advanced glaucoma, and testing should be performed in patients who underwent macular surgery or have fairly advanced glaucoma to determine if ILM peeling should be undertaken.

“Prone positioning after vitrectomy is a long-standing dogma in retinal surgery. However, it might be unrealistic and unnecessary in many cases; but if a gas bubble is present in the eye, surgeons might use it as needed,” he added. “Some patients choose prone position despite the study results suggesting no benefit. However, prone position remains an essential practice in specific cases.”

 

Gaetano R. Barile, MD

E: gaetanobarilemd@gmail.com

This article was adapted from a presentation Dr. Barile delivered at the Precision Ophthalmology 2016 Meeting. Dr. Barile reported no financial interest in any aspect of this report.